Não informado. (1972). Annals of the Research Institute of Epidemiology and Microbiology. Ministery of Public Health.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Annals of the Research Institute of Epidemiology and Microbiology. Sofia: Ministery of Public Health, 1972.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Annals of the Research Institute of Epidemiology and Microbiology. Ministery of Public Health, 1972.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.